Yes, they are. I think that most people still use "may" for present and "might" for past, as well as "may" for more likely and "might" for less likely, but the line's getting blurrier. The biggest difference is that you're better off using "might have" for something that didn't happen, or when combined with other past tenses: "If you had given him a ride, he might have been on time".

Yes they are. 'May' is sometimes considered to be a bit more formal, though.